1. Field of the Invention
This invention relates to incandescent lamps of miniature size, commonly known as Christmas tree lamps, and more particularly to a tester for such lamps.
The small incandescent low voltage, approximately 21/2 volts to 12 volts, lamps commonly called Christmas tree lights or lamps are normally interposed in sockets at selected locations in an electrical series circuit and used for decorations, either indoors or outdoors.
These miniature or "mini" lamps are characterized by a bayonet base approximately 5 mm.times.3 mm.times.6 mm long and in addition to its tungsten illumination element, includes a shunt circuit which provides continuity in the electric series circuit when the incandescent element burns out. Thus, sustaining the continuity of current in the string or circuit, normally some 10 to 50 lamps.
With the loss of the tungsten element in any one mini lamp the rated voltage of the lamp is added and equally distributed to the remaining lamps in that series circuit by the shunt circuit of the burned out lamp.
As tungsten elements burn out in additional lamps, additional voltage is applied to the remaining lamps which is a distinct disadvantage resulting in a further increase of loss of tungsten elements in other lamps.
The voltage then increases to an extent that it destroys the remaining tungsten elements and one or more of the lamp internal shunt.
Attempting to solve the burned out string of lamps by exchanging a new lamp with a bad one and checking lamps along the stringer in domino style, is successful unless at least two lamps have lost their shunt circuit. In the latter case, the domino style of checking lamps in succession will not succeed. It is at this point that the device of this invention may be employed to test the incandescent element and shunt circuit of each burned out lamp, including the blinker control if one is used.
2. Description of the Prior Art
The most prior patent is believed to be U.S. Pat. No. 3,725,780. This patent provides a container supporting a 9-volt battery connected by wiring with a pair of lamp or bulb testing terminals each terminal being formed by a plurality of juxtaposed electrical current conducting bristles arranged in opposition so that the base or contacts of a miniature lamp may be contacted when the base or screw end of the bulb is inserted between the bristle terminals to determine whether or not the bulb element is burned out.
This invention is distinct over this patent and other lamp testing patents by providing an internal electrical current-excited tungsten element including a shunt which not only indicates whether or not the tungsten element under test is burned out or if its shunt circuit is still intact or broken by the illumination or nonillumination of the tester contained control element.